Sister: Princess Diana Feared Dodi's Father Was Spying on Her

Princess Diana feared her boyfriend's father was spying on her as the couple took a luxurious Mediterranean cruise, Diana's sister said Monday.

The princess believed the yacht she and Dodi Fayed were vacationing aboard had been bugged by Dodi's father, Mohammed Al Fayed, her sister Lady Sarah McCorquodale told an inquest investigating Diana and Dodi's deaths.

"She thought the boat was being bugged by Mr. Al Fayed senior," McCorquodale said, telling the court that Diana shared the concern during a phone conversation from the yacht. McCorquodale said she assumed the princess was talking over a mobile phone.

Diana, Dodi Fayed, and their driver, Henri Paul, died in Paris after their car slammed into a pillar in the Pont d'Alma tunnel on August 31, 1997. While French and British investigators blamed Paul for the crash, Mohammed Al Fayed maintains the couple was the victim of plot carried out by rogue intelligence agents and masterminded by Prince Philip, Queen Elizabeth II's husband.

Much of the testimony at the inquest has centered on the question of whether or not anyone was eavesdropping on the princess, and the nature of her relationship with Philip, her father-in-law at the time she was married to Prince Charles.

Earlier Monday, a British detective said a box allegedly containing letters addressed to the princess from Philip remains missing.

Acting Detective Inspector Roger Milburn said the whereabouts of the box, which he said contained correspondence between the two, remained "an unanswered question."

McCorquodale also said she had no idea where the letters had gone.